The invention relates to a convoluted boot for sealing an annular gap between two parts which are connected to one another in a rotationally fast way, which can be articulated relative to one another and which are axially displaceable relative to one another. In particular, the invention relates to a constant velocity plunging joint, having a low-strain hard polymer material, with a first larger collar to be secured to a first component, a second smaller collar to be secured to a second component and a plurality of annular fold units which extend between the first collar and the second collar. The fold units are provided in the form of outer folds which include two annular flanks and each form a fold peak between two fold valleys.
Because requirements become more and more stringent, convoluted boots of said type are produced from hard polymer materials to an increasing extent. As compared to soft resilient materials used earlier, said hard polymer materials feature an improved resistance in mechanical and chemical respects, and in view of higher speeds and the need for a longer service life, it is inevitable that they are used. One concern is their reduced flexibility which can be a problem at low temperatures. In the case of constant velocity fixed joints which effect articulation only between two rotating components, convoluted boots made of said materials, even today, do meet the respective requirements in their entirety. In the case of constant velocity plunging joints which, in addition to the angular movement, effect an axial displacement between the two rotating components, this means that the sealing convoluted boots are subject to friction contact between the annular flanks on the inside of the angle when the joint is in a telescoped and articulated condition and, when the joint is in the extended and articulated condition, the individual annular folds open up excessively widely on the outside of the angle, causing a collapsing of the annular folds or other irregularities. At high speeds, in particular, this can result in the elasticity limit of the convoluted boot being exceeded and it can lead to boot damage.